OLED (Organic Light Emitting Diode) display, which is provided with an extremely thin organic material coating and a glass substrate, can achieve self-illumination, since the organic material may illuminate when the current pass through it. The OLED display has attracted considerable attention duo to the advantages such as wide viewing angle, significant power saving, simple structure and high quality dynamic picture.
Currently, the OLED display is gradually mass produced. Particularly, the research on the large size AMOLED (Active Matrix Organic Light Emitting Diode) display is becoming a hotspot, and then the EL (electroluminescent) module used in AMOLED display is also becoming a main research object. In the conventional process, organic film used in the luminescent layer of the EL module is formed by evaporation. In conventional evaporation process, the evaporation source is a single point source, from which the organic molecules are gasified or sublimated without directionality. The proportion of the material coated on the substrate to the material evaporated is very low, because many sublimated molecules are attached to the evaporation chamber rather than on the substrate. Moreover, it is difficult to form a uniform film by the single point source, because the distance between the evaporation source and the coating position varies with the change of the coating position on the substrate.
It is required to provide an evaporation apparatus by which a large area organic film can be formed with high accuracy, because the uniformity of the film has a great influence on the brightness and the chromaticity of luminescence. In the conventional technology, an apparatus for coating a large area film comprises: a container 24, an evaporated steam flow adjustor 25 and a top plate 26 (as shown in FIG. 1). In addition, the apparatus further comprises a heating device (not shown in FIG. 1). The evaporated steam flow adjustor 25 has a porous layered structure and is disposed between the container 24 and the top plate 26. The evaporated steam flow adjustor 25 is used to control the flow and the direction of the evaporated steam and enlarging the steam distribution area, so as to spray the steam uniformly onto the substrate for providing a planar film formed of sprayed spots. The overlapped deposition area of spray nozzles 261 can be adjusted by changing the distribution and diameter of the spray nozzles 261. However, because the accuracy of deposition cannot be improved by above apparatus and process, the serious waste of organic material has not been avoided and the deposition rate has not been improved yet.
Therefore, selecting for appropriate organic materials and designing a more efficient deposition apparatus, which are beneficial to improve the utilization and the accuracy of the organic materials deposition, become the focus of researcher and manufactory. However, during the conventional process for coating an organic material, the deposited pattern is significantly deformed and is not uniform at all due to the dimensional error and the low accuracy of the mask, thus, the pixel crosstalk and short circuit may occur, the deposition accuracy and the defect-free rate may be further decreased.